Internships are a part of the college experience for many students, and on Thursday organizations tried to show their appreciation on social media for National Intern Day.

However, as blogger Charles Clymer pointed out, internships often require students to work for little to no money.

Though she’s now a senior White House advisor, a 2016 tweet from Ivanka Trump’s account boasted about the unpaid interns she used at her New York City fashion and jewelry company. The account used the hashtag #nomoneynoproblems.

But for low-income students, unpaid internships are a big problem. Although the legality of unpaid internships is disputed, companies still rely on them, and there’s some evidence that they put poorer students at a disadvantage in the workplace, thus reducing socioeconomic diversity.

Some students can’t afford to accept an internship.

“You can’t bring people to a city like Washington, D.C., or New York, or San Francisco, where a lot of internships are, and not pay them,” Maxwell Love, president of the United States Student Association told the Atlantic in 2015. Indeed, even most paid internships don’t pay enough to cover the high cost of living.

David Dennis wrote an opinion piece for The Guardian about all the ways internships create a class system within the media, in particular.

“Does your publication use unpaid interns as the prevalent mode of determining full-time jobs?” he asked. “If so, then I’m sorry to inform you that your publication is perpetuating a privilege-based upward mobility, and it’s ruining journalism.”

Dennis said media internships are nearly impossible for low-income students to accept, and it shows up in the product.

“As a consumer, I find opinions or perspectives reflecting my own come few and far between,” he wrote. “How many journalists can say they have firsthand knowledge of the mentality of someone from the inner-city? Many of these voices have been muted just because they simply can’t navigate the landscape of privilege that most modern journalism encourages.”

Even the interns who can afford to accept an unpaid internships are at a disadvantage.

A 2016 post from the Economic Policy Institute said there’s evidence that unpaid interns struggle more than paid interns in the job market. Data from the The National Association of Colleges and Employers (NACE) Student Survey Report showed that the job offer rate for interns who had a paid internship at a for-profit company was 72 percent, while unpaid interns only got job offers 44 percent of the time. Unpaid interns also received much lower salary offers.